The present invention is related to methods and apparatus for clearing blocked natural and synthetic vessels, and more specifically, to methods and apparatus for percutaneously clearing material from vessels with a rotating device and suction.
A variety of techniques and instruments have been developed for use in the removal or repair of obstructive material in vessels and other body passageways. Such material may include atheromas, thrombi, or emboli. An atheroma is a mass of plaque of degenerated, thickened arterial intima occurring in atherosclerosis. A thrombus is an aggregation of blood factors, primarily platelets and fibrin with entrapment of cellular elements, frequently causing vascular obstruction at the point of its formation. An embolus is a clot or other plug brought by the blood from another vessel and forced into a smaller one, thus obstructing the circulation.
Many catheter-mounted devices are presently available for removing material from vessels. Some of these devices include rotatable abrasive members on the distal tip of a flexible catheter, which tend to remove hardened atherosclerotic materials without damaging the normal elastic soft tissue of the vessel wall.
Another material removal device is seen in the U.S. Pat. No. 5,423,799 to Shiu, and includes a tubular housing mounted on the distal end of a catheter within which a helical screw member rotates. The screw includes a sharp edge which, in cooperation with housing, cuts the tissue and draws it into the housing for later removal.
Despite advances made in catheter-mounted material removal devices, many of them remain limited in their operational capacity, and tend to clog up fairly quickly. This necessitates the surgeon advancing very slowly through the material blockage, and greatly increases the length of surgery. In the worst-case, the device becomes irreversibly clogged, and must be removed and another device procured and substituted. Therefore, there remains a need for a more efficient catheter-mounted material removal device that can rapidly cut through a mass of blocking material without clogging.
In one embodiment, the present invention provides a device for removing material from a body lumen including an elongate, flexible tube having distal and proximal ends and a passageway therethrough. The device has a material removal tip on the distal end including an outer housing rotationally fixed with respect to the tube and a rotating member within the housing. The housing includes a lumen extending from a distal open mouth to the tube passageway. The rotating member includes distal and proximal ends, a central body, and a plurality of circumferentially spaced flanges extending radially outward from the body. At least one shearing member is formed within the lumen of the housing and axially adjacent to the flange to cooperate with the flange and shear material received in the housing mouth. The shearing member may be located distally or proximal with respect to the flanges, or shearing members on both sides of the flanges may be provided. The housing desirably includes proximal and distal sections, each including lumens, and an annular groove larger than either the distal or proximal sections and formed therebetween for axially restraining the flanges on the rotating member. The shearing member is preferably located adjacent to the groove. The housing may be formed in one piece or two separate pieces.
In a preferred embodiment, the rotating member has a central body and a helical screw thread thereon and is driven by a drive shaft that extends through a catheter attached to the housing. The shearing member has a radial dimension that brings it into close proximity with an associated rotating member. That is, a distal shearing member is sized to come into close proximity with the central body of the rotating member, while a proximal shearing member is sized to come into close proximity with a drive shaft.
In another aspect, the present invention provides a material removal tip for use in a catheter-mounted material removal device, comprising a rotatable member having an outwardly projecting shearing member, and a generally tubular housing sized to receive the rotatable member. The housing includes a stationary shearing member located axially adjacent to the rotating shearing member. The stationary and rotating shearing members cooperate to chop material received within the housing, reducing the clogging propensity of the material. There is preferably a plurality of rotating shearing members axially restrained within a groove formed on the inner surface of the housing. The stationary shearing member is desirably located adjacent to groove, either proximally, distally, or both in the case of two stationary shearing members.
The present invention further provides a method of material removal, including advancing through a body lumen a catheter-mounted material removal device having distal material removal tip including a hollow housing and a rotatable member therewithin. The rotatable member is rotated to engage the material, which is then sheared in the housing between relatively rotating shearing members to reduce the clogging propensity of material. Subsequently, the sheared material is removed from within the housing as the device is further advanced through the body lumen.